Prevalence of Giardia duodenalis among African children: A systematic review and meta-analysis

Background Giardia duodenalis (G. duodenalis) is one of the major causes of diarrhea among children. We performed a systematic review and meta-analysis to assess the prevalence of G. duodenalis and associated risk factors among African children. Methods We searched online databases (PubMed, Scopus, and Web of Science) as well as the Google Scholar search engine for studies measured the prevalence of G. duodenalis among African children, published between 1 January 2000 and 15 March 2022. Due to high heterogeneity among the included studies, a random-effects meta-analysis model was employed to estimate pooled prevalence and 95% confidence intervals (CI). Results A total of 114 articles from 29 African countries met the inclusion criteria. The pooled prevalence of G. duodenalis infection among African children was estimated as 18.3% (95% CI: 16.5–20.2). The highest and lowest pooled prevalence of G. duodenalis infection were estimated in Niger and Cameroon as 65.1% (55–75.2) and 0.08% (0.02–1.05), respectively. Considering the type of study population, the highest prevalence was related to, iron-deficient children 65.2% (61.3–69.1), handicapped children 30.4% (18.3–42.4), HIV infected children 25.7% (11.2–40.2) and displaced children 20.2% (16.5–23.9). Conclusions Giardiasis is common among African children, hence, prevention and control scheme of this protozoan in children should be considered by health officials and health policymakers, especially in African countries where prevalence is highest.

Children are more exposed to different environmental sources (e.g., playing with soil) and also have immature immune systems to fight infections (Moya et al., 2004;Mussi-Pinhata and Nascimento, 2001).Therefore, children have a higher probability of contracting infectious agents.Determination of the epidemiological patterns of G. duodenalis infection is necessary to design future control programs and preventive measures to reduce the incidence of the infection.To address this gap, we designed a systematic review and meta-analysis to assess the prevalence of G. duodenalis and associated risk factors in African children.

Information sources and systematic search
The present systematic review and meta-analysis was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) protocol (Moher et al., 2015).Published articles on the prevalence of G. duodenalis in African children was gathered through three international databases (i.e.PubMed, Scopus, and Web of Science) and Google Scholar search engine between 1 January 2000 and 15 March 2022.The search process was accomplished using Medical Subject Headings (MeSH) terms alone or in combination: ("Intestinal protozoa" OR "Giardia" OR "Giardiasis") AND ("Prevalence" OR "Epidemiology") AND ("Children").Moreover, the references list of all selected articles was hand-searched to find other relevant articles or their citations by searching in Google Scholar.

Inclusion criteria, study selection and data extraction
To assess the article eligibility based on determined inclusion criteria, all papers were reviewed by two independent reviewers and possible contradictions among studies were removed by discussion and consensus.The inclusion criteria for this systematic review were as follows: (1) full-texts or abstracts published in English from Africa continent; (2) peer-reviewed original research papers or short reports; (3) cross-sectional studies that estimated the prevalence of Giardia in children population (≤18 years); (4) utilizing fecal microscopy, coproantigen or molecular diagnostic methods; (5) reports with information on the total sample size and positive samples; and (6) published online from 1 January 2000 and 15 March 2022.Those papers without full-text accessibility or papers that did not meet the above criteria were excluded.Next, the desired data were gathered precisely using a data extraction form including, the first author's last name, the year the study was conducted and the publication year, countries, provinces and cities, types of method used, total sample sizes, number of positive samples, types of children, gender and age of children.

Study quality assessment
The Joanna Briggs Institute (JBI) checklist was applied for the risk of bias (internal validity) assessment of the included articles (Porritt et al., 2014).This checklist comprises ten questions with four options including Yes, No, Unclear, and Not applicable.Summary, a study can be awarded a maximum of one star for each numbered item.The papers with a total score of 4-6 and 7-10 points were specified as the moderate and high quality, respectively.Based on the obtained score, the authors have decided to include (4-10 points) and exclude (≤3 points) the papers.

Meta-analysis
For each included study, the point estimates and their respective 95% confidence intervals (CI) using a random effect model (REM) were calculated.The REM allows for a distribution of true effect sizes between articles.To visualize possible heterogeneity among included studies the forest plot analysis was used.The heterogeneity index among the included studies was defined using the I 2 index and Tau squared to reveal the variation in study outcomes between individual studies (Barati et al., 2022;Maleki et al., 2021).The univariate and multivariable meta-regression analysis was used to estimate the effects of probable factors in heterogeneity (Barati et al., 2022).To investigate the effect of each study on the pooled estimation of prevalence, the sensitivity analysis method was used by removing studies one by one.The robustness of each model was evaluated and finally, the most favorable model was chosen.
Using sub-group analyses, the pooled prevalence of Giardia infection was estimated according to countries, types of diagnostic methods, types of children, and periods of studies.An odds ratio (OR) (and the corresponding 95% (CI)) was calculated for each study to assess the association between Giardia spp.prevalence and risk factors such as sex (male and female) and place of living (rural and urban).
The publication bias was evaluated with Egger's regression test and interpretation of the funnel plot in this meta-analysis and the trim-and-fill method was used to estimate the number of censored studies and correct the overall estimate (Barati et al., 2022).
Moreover, due to different sensitivities and specificities of diagnostic methods, we assumed that our results would be "apparent" prevalence rates, and did not represent true prevalence rates.The prevalence of G. duodenalis in children in different countries from Africa was demonstrated as a world map using ArcGIS 10.3 software (https://www.arcgis.com).Source of vector map is from ESRI (www.esri.com/en-us/home).This meta-analysis was conducted with the Stata version 16 software and the trial version of Comprehensive Meta-Analysis software vs. 3.A P-value of <0.05 was considered significant.

Characteristics of the eligible studies
A flowchart depicting the identification process of qualifying studies is presented in Fig. 1.In brief, the systematic search identified 4702 potentially relevant articles.After removing duplicates and/or non-eligible papers, 114 articles from 29 countries across Africa met the inclusion criteria in the systematic review and meta-analysis.The countries with the highest number of studies were Ethiopia (17.54%; 20/114 studies) and Egypt (16.66%; 19/114 studies).The main characteristics of each study are shown in the Supplementary Table 1.The results of quality assessment according to JBI with references for eligible studies are depicted in Supplementary Table 1.The included articles in the present meta-analysis showed an acceptable quality.

The pooled prevalence of G. Duodenalis in children
A total of 63,165 children were evaluated in 114 studies regarding the prevalence of G. duodenalis in African children, of which S. Kalavani et al. 10,202 were diagnosed as infected based on diagnostic criteria.After performing sensitivity analysis by removing one-by-one studies and selecting the robustness model, the overall prevalence of G. duodenalis infection in African children was estimated at 18.3% (95% CI,16.5-20.2) using the REM (Supplementary Fig. 1).
According to the heterogeneous assessment indicators between studies (Q value = 11,448.44,d.f.= 113, p < 0.0001, I 2 = 99.0%,Tau squared = 0.0097), it was shown that there is a high heterogeneity between the studies included in this meta-analysis.In the next step, multivariable and univariate meta-regression models were used to find the origin of heterogeneity (Table 1).Multivariable metaregression analysis showed that the type of population studied in children it may be the source of heterogeneity (p = 0.037), however, this analysis did not show significant heterogeneity in the quality of the studies included in the meta-analysis, study location, sample size, diagnostic methods, and age groups (P > 0.05) (Table 1).In addition, the univariate meta-regression model showed that the location of the study (country) (p = 0.006) and the type of population under study (p = 0.004) may be the causes of heterogeneity (Table 1).
The subgroup meta-analysis using the REM was used to estimate the overall prevalence in groups including country, type of study population, year of publication, detection method, and age group (Table 2).According to the location of the study, the highest prevalence of G. duodenalis was in African children in Niger 65.1% (55-75.2),Algeria 54.5% (1.04-98.07),Senegal 45.2% (40.4-50.1),and Guinea-Bissau 40.6% (30.9-50.2),respectively.On the other hand, the lowest prevalence was related to Cameroon 0.08% (0.02-1.05), and the Central African Republic 0.09% (0.001-1.09) (Table 2 and Fig. 2).

Publication bias
Egger's regression test and asymmetry in the funnel plot displays that there is significant publication bias for included studies in this meta-analysis (bias = 10.018,95%CI: 7 7.941-12.096,P < 0.001) (Fig. 5).Therefore, the trim-and-fill model using non-parametric methods was used for correction the meta-analysis.This model showed that 54 hypothetical studies about the prevalence of G. duodenalis in African children were censored in this meta-analysis.Consequently, the pooled prevalence of G. duodenalis corrected by the REM based on the trim-and-fill model was estimated to be 4.09% (95%CI: 2.09-7.0).

Discussion
This is the first study to estimate the prevalence of G. duodenalis among African children.The prevalence obtained for G. duodenalis  in the meta-analysis were relatively high, especially in studies that have used the Real-time PCR method (Table 2).Conventionally, microscopy detection method using staining procedures is considered as the gold standard method for the detection of cysts and/or trophozoites of G. duodenalis (Soares and Tasca, 2016).However, molecular methods are preferred for conducting research activities because they have higher sensitivity and specificity and the interpretation of results is easier (David and Ap, 2006;Elmi et al., 2017).Accordingly, the pooled prevalence provided by molecular methods could be closer to the true prevalence.For a deeper understanding of this issue, it is necessary for researchers to use molecular methods in addition to microscopy methods.By considering the prevalence of G. duodenalis in different African countries, the highest infection rates were found in Niger (one study with pooled prevalence of 65.1%) and Algeria (two studies with pooled prevalence of 54.5%).By contrast, infection rates in Cameroon (one study with pooled prevalence of 0.08%) and Central African Republic (one study with pooled prevalence of 0.09%) countries were low.Several environmental and sociodemographic parameters are complicated in the different prevalence rates obtained, including climatic condition, parasite control measures, HDI, and the use of diverse diagnostic methods in different regions (Barasa et al., 2024;Kalavani et al., 2024;Koh et al., 2024;Weitzel et al., 2024).In addition to all these factors, it is necessary to conduct more studies in African countries and some countries that have not done any research on this issue should consider it; finally, a deeper understanding of its prevalence in children in different parts of Africa can be obtained.
Considering the year of publication (Table 2), the prevalences in different time periods from 2000 to 2022 were almost similar.Therefore, the results of this meta-analysis study, especially the pooled prevalence rates based on the year of publication, should be interpreted with caution.Hence, factors such as the number of published articles and the sample size of studies each year may play a role in causing heterogeneity.
Living in a rural area compared to an urban area, and boys compared to girls increased the chance of contracting G. duodenalis by 1.24 and 1.26 times, respectively, which might be explained by lower personal hygiene scores and more contact with G. duodenalis cysts-contaminated water and vegetables.
The present study has a number of limitations.First, despite our comprehensive search, there was a paucity or absence of data for a number of countries, and many of the available studies had limited sample sizes and a lack of data on socio-demographic and/or risk NA: Not applicable, ELISA: enzyme-linked immunosorbent assay; PCR: polymerase chain reaction.
S. Kalavani et al. factors.Moreover, in some countries only one or two eligible studies was identified, which could compromise somewhat the interpretation of present estimates.Second, studies included were undertaken during different time periods, with an absence of recent data for some countries, limiting the accuracy of inter-regional comparisons.Third, there was a high heterogeneity in this meta-analysis.
Although we investigated its possible source by performing meta-regression analysis.

Conclusions
In summary, prevention and control scheme of G. duodenalis in children should receive greater attention by health officials and health policymakers, especially in African countries where prevalence is highest.Also, we recommend that periodic screenings for G. duodenalis in such countries should be incorporated into the routine clinical care of iron-deficient children, handicapped children, HIV infected children, and displaced children.

Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.S. Kalavani et al.

Table 1
Result of multivariable and univariate meta-regression model to identify possible sources of heterogeneity.

Table 2
The overall Prevalence G. duodenalis in African children.